This invention relates to a multiplexable sensor that has two terminals through which it may be energized and addressed and through which it may respond upon being addressed.
Multiplexable sensors of the prior art capable of some or all of these functions have been employed in automobiles or other vehicles wherein many similar sensors are energized from a common DC voltage source so as to require few wires, preferably only one wire, and a chassis ground connecting all the sensors. The sensors may be capable of detecting light, nuclear radiation, a magnetic field, an electrified open circuit or closed circuit, etc. whereby the transducer incorporated in the sensor converts one of those kinds of energy to an electrical signal. Such sensors are capable of detecting the presence or absence of fields having a predetermined minimum field strength, a particularly useful feature when used to detect vehicle performance or functions such as low fluid levels, low fluid pressuresm low or high temperature, etc.
Particularly, it is known to use an integrated circuit Hall switch as a proximity detector which is readily used to detect discrete levels whereby the position of a magnet carrying float is monitored by the IC Hall switch. Such a liquid level detector is described by Dumery in U.S. Pat. No. 4,589,282 issued May 20, 1986. Also, a simple two-terminal Hall switch sensor is described by Avery in U.S. Pat. No. 4,374,333 issued Feb. 15, 1983. Both patents are assigned to the same assignee as is the present invention.
It is an object of the present invention to provide a two-teminal-multiplexable sensor having a low standby or quiescent current drain; namely, current drain when the sensor is not addressed.